1. Field of the Invention
The present invention relates to a process for the preparation of a phenylhydrazine or an inorganic acid salt thereof of the formula (1): wherein X is a hydrogen atom or a halogen atom; Y is a halogen atom; and W is a hydrogen atom or —ZR in which Z is an oxygen atom or a sulfur atom, and R is a hydrogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C3-C8 cycloalkyl group, a benzyl group, a C3-C6 alkenyl group, a C3-C6 haloalkenyl group, a C3-C6 alkynyl group, a cyano-C1-C6 alkyl group, a C2-C8 alkoxyalkyl group, a C2-C8 alkylthioalkyl group, a carboxy-C1-C6 alkyl group, (C1-C8 alkoxy) carbonyl-C1-C6 alkyl group, a [(C1-C4 alkoxy)-C1-C4 alkoxy]carbonyl-C1-C6 alkyl group, (C3-C8 cycloalkoxy)carbonyl -C1-C6 alkyl group or a [(C1-C6 alkoxy)carbonyl-C1-C6 alkyl]oxycarbonyl-C1-C6 alkyl group.
A phenylhydrazine of the formula (1) is a useful intermediate for the preparation of, for example, pyridazin-3-on compounds of the formulae (4): which have good herbicidal activities.
2. Prior Art
JP-A-9-323977 describes that a phenylhydrazine of the above formula (1) is synthesized by diazotizing an aniline derivative of the formula (3): wherein X, Y and W are the same as defined above, and then reducing the diazotized compound with tin chloride.
However, the above synthesis process has drawbacks such that a reaction mixture has low filterability when insoluble tin-containing by-products are removed by filtration after the reaction, since the reduction is performed with tin chloride, and that tin compounds should be treated after the reaction. Therefore, such a synthesis process may not be industrially preferred. Thus, it is highly desired to develop a new synthesis process of a phenylhydrazine or an inorganic acid salt thereof of the formula (1) using no metal reducing agents.